Stihl FS 50 Manual

The Stihl FS 50 is a lightweight, easy-to-use gasoline-powered string trimmer designed for residential lawn and garden maintenance. It features a reliable 2-stroke engine, a straight shaft, a loop handle with integrated controls, a Tap 'n Go™ semi-automatic line advance system, and a PolyCut™ head. Below are key sections for safety, features, operation, maintenance, and troubleshooting.

Features at a Glance

Key components: 2-stroke engine, straight shaft, loop handle with throttle trigger and stop switch, PolyCut™ head, Tap 'n Go™ line advance, fuel tank, and spark plug.

Feature	Description
Engine	STIHL 2-stroke, single-cylinder, air-cooled
Displacement	27.2 cm³ (1.66 cu. in.)
Powerhead Weight	Approx. 4.6 kg (10.1 lbs)
Shaft	Straight, solid drive shaft
Handle	Loop handle with integrated controls
Cutting Attachment	PolyCut™ head with Tap 'n Go™ line advance
Fuel Tank Capacity	Approx. 0.35 L (11.8 fl. oz.)
Throttle Trigger	With throttle trigger lockout
Stop Switch	Slide switch for engine stop
Starter	STIHL Easy2Start™ system (if equipped)

Safety Information

Read and understand all instructions before operation. Wear appropriate personal protective equipment (PPE).

1. Always wear eye protection, hearing protection, long pants, sturdy boots, and gloves.
2. Inspect the trimmer before each use for loose parts or damage.
3. Clear the work area of bystanders, pets, and obstacles.
4. Operate only in well-ventilated areas; be aware of fire hazards.
5. Never operate the unit with a damaged or missing guard.

WARNING! Risk of serious injury or death from rotating cutting head, thrown objects, fire, or carbon monoxide. Follow all safety rules.

Assembly & First Use

Assemble the trimmer and prepare for first start-up.

1. Attach the handle: Secure the loop handle to the shaft as per instructions.
2. Install the cutting attachment: Attach the PolyCut™ head to the drive shaft and secure.
3. Fill with fuel: Use STIHL MotoMix® premixed fuel or mix STIHL 2-stroke oil with unleaded gasoline (50:1 ratio).
4. Starting the engine: Place on firm ground, set stop switch to "I", press throttle trigger lockout, pull starter rope briskly.
5. Warm-up: Allow engine to idle for a short period before use.

CAUTION! Use only STIHL-approved fuel and lubricants. Ensure all fasteners are tight.

Specifications

• Model: STIHL FS 50.
• Engine Type: 2-stroke, single-cylinder, air-cooled.
• Displacement: 27.2 cm³ (1.66 cu. in.).
• Power Output: Approx. 0.8 kW (1.1 hp).
• Idle Speed: 2,800 rpm.
• Maximum Engine Speed: 12,500 rpm.
• Fuel/Oil Ratio: 50:1 (STIHL 2-stroke oil).
• Fuel Tank Capacity: 0.35 L (11.8 fl. oz.).
• Sound Pressure Level: Approx. 94 dB(A).
• Vibration Levels: Left/Right handle: < 2.5 m/s².
• Cutting Swath: Approx. 43 cm (17 in.) with standard line.

Controls and Operation

Loop Handle: Throttle trigger with lockout, stop switch. Shaft: Drive shaft inside. Cutting Head: PolyCut™ head.

Operation: Hold trimmer with both hands, right hand on throttle trigger, left hand on handle. Keep cutting head parallel to ground and swing in an arc. Use Tap 'n Go™: Tap head on ground at idle to advance line.

Adjusting Handle: Loosen clamp to rotate handle for comfortable operation. Stop Switch: Slide to "0" to stop engine.

Fuel & Lubrication

Use fresh, unleaded gasoline with a minimum octane rating of 89 (RON). Mix with STIHL 2-stroke engine oil at 50:1 ratio (or use STIHL MotoMix®).

1. Fuel Mixing: Pour oil into clean fuel can, add gasoline, close and shake well.
2. Filling: Clean area around fuel cap, fill tank to about 80% capacity.
3. Gearbox Lubrication: Lubricate gearbox at shaft end with STIHL grease periodically.

Tip: Never use fuel older than 30 days. Store fuel in approved container.

Cutting Attachment

PolyCut™ head with Tap 'n Go™ line advance system.

1. Line Replacement: Remove spool, wind new line (max. length as specified), reassemble.
2. Line Advance: While engine is idling, tap cutting head firmly on ground to advance line.
3. Cutting Technique: Use tip of line for cutting; avoid forcing into hard objects.
4. Head Inspection: Regularly check for wear, cracks, or damage; replace if necessary.

WARNING! Always stop engine before inspecting or servicing cutting attachment. Wear gloves.

Maintenance

Regular maintenance ensures long life and safe operation.

Item	Interval	Action
Air Filter	Every 10 hours	Clean with soapy water; replace if damaged.
Spark Plug	Every 50 hours	Clean electrode, check gap (0.5 mm / 0.020 in.), replace if worn.
Fuel Filter	Every season	Replace in-tank fuel filter.
Gearbox	Every 25 hours	Lubricate with STIHL grease.
Exhaust Ports/Screen	Every 50 hours	Clean carbon deposits.
External Cleaning	After each use	Wipe with damp cloth; remove debris.

CAUTION! Disconnect spark plug boot before performing maintenance.

Storage

Prepare trimmer for storage if not used for more than 30 days.

1. Drain fuel tank and run engine until it stops to empty carburetor.
2. Remove spark plug, add a few drops of oil into cylinder, pull starter slowly to distribute, reinstall plug.
3. Clean entire unit thoroughly.
4. Store in a dry, secure place, out of reach of children.

CAUTION! Never store unit with fuel in tank indoors or in enclosed spaces.

Regulatory Information

This product complies with applicable emissions and safety standards. STIHL is a registered trademark. The engine exhaust from this product contains chemicals known to the State of California to cause cancer, birth defects, or other reproductive harm. For genuine STIHL parts and service, contact an authorized STIHL servicing dealer. For support, visit www.stihlusa.com or call 1-800-467-8445.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Engine does not start	No fuel, flooded, spark plug	Check fuel; wait if flooded; check/replace spark plug.
Engine runs poorly/dies	Clogged air/fuel filter, carburetor	Clean/replace air filter; check fuel filter; adjust carburetor (by dealer).
Line does not advance	Empty spool, tangled line	Refill line spool; disassemble and rewind line properly.
Excessive vibration	Damaged cutting head, loose parts	Inspect head for damage; tighten all fasteners.
Loss of power	Clogged exhaust, worn engine	Clean exhaust ports/screen; seek dealer service.

Service: For repairs beyond basic maintenance, contact an authorized STIHL dealer.

Support: 1-800-467-8445; www.stihlusa.com